Semiconductor-based detection and decontamination system

ABSTRACT

A system and method for identifying and making quantitative determinations of different deposits on a portion thereof, determining that the deposit is a contaminant and decontaminating at least the portion of the system is disclosed. The system comprises a controller, a sensing portion and a decontamination portion. The controller contains information about at least one noncontaminant. The sensing portion communicates with at least the controller and the portion of the system and is adapted to detect the deposit. The decontaminating portion communicates with at least the controller and is adapted to decontaminate the portion of the system.

PRIORITY CLAIM

This divisional application claims the benefit of U.S. patentapplication Ser. No. 11/443,955, filed on May 31, 2006 presentlypending, the entirety of which is incorporated herein.

CONTRACTUAL ORIGIN OF THE INVENTION

The United States Government has rights in this invention pursuant toContract No.: W-31-109-39-ENG between the Government and the Universityof Chicago representing Argonne National Laboratory.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to a detection anddecontamination system and method. More specifically, embodiments of thepresent invention relate to a system and method for rapidly andaccurately detecting, characterizing, quantifying, and decontaminatingorganics present in the atmosphere due to chemical and/or biologicalspills, weapons, terrorist attack and/or other releases.

2. Background of the Invention

In the event of a chemical and/or biological spill, weapon, terroristattack and/or release, rapid detection, characterization,quantification, and decontamination is crucial. Commercially availablesensors and sensing technologies provide for detecting contaminants onthe surface of an object. However, these sensors and technologiesgenerally require collecting a sample of the contaminant which must thenbe transported to a remote instrument for contaminant identification andconcentration determination.

Photocatalytic agents are effective for removing organic pollutants inboth aqueous and gaseous environments. Heterogeneous semiconductorphotocatalysis relies upon photoactive semiconductors, such as titaniumdioxide (TiO₂) for example, to not only sorb noxious and pollutantgaseous emissions, but to photocatalyticaly oxidize or reduce suchemissions into less toxic organics and carbon dioxide.

As illustrated in Equation 1 below, when TiO₂ is illuminated by lighthaving energy hv equal to or exceeding the TiO₂'s bandgap energy (3.2electron volts for anatase TiO₂), electrons (e−) are excited (promoted)into the conduction band. Electron promotion creates positive holes (h⁺)in the valence band. If these electron-hole pairs do not recombine toproduce heat (as illustrated in Equation 2 below), the pairs promoteoxidative and reductive electron transfers as shown in Equations 3through 7 (adapted from Chemical Engineering Science, Vol. 56, 1561[2001]).

TiO₂ +hv→TiO₂(h ⁺ +e ⁻) electron-hole pair formation  Eq. 1

e ⁻ +h ⁺→heat recombination  Eq. 2

e ⁻+M^(n+)→Mn^((n−1)+) reduction  Eq. 3

h ⁺+H₂O_((ads)).OH+H⁺ oxidation of adsorbed (abs) water  Eq. 4

h ⁺+2OH_((ads)) ⁻→.OH+OH⁻ oxidation of adsorbed hydroxide ions  Eq. 5

.OH+R_((ads))→.R_((ads))+H₂O organic oxidation  Eq. 6

.R+(.OH,.R_(ads))→products termination  Eq. 7

-   -   where hv=light energy, h⁺=positive holes, e⁻=electrons,        M^(n+)=oxidized compound and R_((abs))=the absorbed organic        species or moiety.

The charges in the valence and conduction bands can oxidize and reducemoieties at the TiO₂ surface. In addition, the positive holes oftenreact with water or hydroxyl ions sorbed to TiO₂, producing hydroxideradicals which, in turn, oxidize absorbed organic moieties.

TiO₂ has been found to be an effective oxygen sensor, since the oxygendiffuses into TiO₂ oxygen vacancies, thus increasing the TiO₂resistivity. This is especially true at elevated temperatures. See, forexample, A. Rothschild, et al. “Sensing Behavior of TiO₂ Thin FilmsExposed to Air at Low Temperatures,” Sensors and Actuators B, Vol. 67,282 (2000); R. K. Sharma, et al., “Influence of Doping on Sensitivityand Response Time of TiO₂ Oxygen Gas Sensor,” Review of ScientificInstruments, Vol. 71, 1500 (2000); and N. Golego, et al., “SensorPhotoresponse of Thin-Film Oxides of Zinc and Titanium to Oxygen Gas,”J. Electrochem. Soc., Vol. 147, 1592 (2000).

TiO₂ thin films have been used, at elevated temperatures (100° C. to500° C.), to detect different types of alcohols including ethanol,methanol and propanol. See, for example, G. Sbeerveglieri, et al.,“Titanium Dioxide Thin Films Prepared for Alcohol MicrosensorApplications,” Sensors and Actuators B, Vol. 66, 139 (2000).

Resistivity changes occur when gases chemisorb onto the TiO₂ surface.Such resistivity changes have been used to derive current, phase lag,and surface potential interactions, producing one-point relationshipsunique to the individual compounds sorbed onto the TiO₂. See, forexample, M. R. Islam, et al., “Chemical Sensor Based on Titanium DioxideThick Film: Enhancement of Selectivity by Surface Coating,” Appl.Surface Sci., Vol. 142, 262 (1999).

The chemisorption of compounds onto the TiO₂ surface has also been usedto capture distinct responses from applied sinusoidal voltages on rutileTiO₂ films in the presence of various organic gases. These responseswere enhanced in the presence of 700 nanometer (nm) light. See, forexample, N. Kumazawa, et al., “Photoresponse of a Titanium DioxideChemical Sensor,” J. Electro. Chemistry, Vol. 472, 137 (1999).

U.S. Pat. No. 6,203,678 issued on Mar. 20, 2001 to Leonhard, et al.discloses a galvanic solid electrolyte sensor for measuring gaseousanhydrides. The sensor includes a ceramic solid electrolyte, a measuringelectrode, and a spatially separated reference electrode.

U.S. Pat. No. 5,989,990 issued on Nov. 23, 1999 to Koh, et al.,discloses a method for fabricating a tin oxide thin-film sensor using anion cluster beam deposition (“ICBD”) process.

U.S. Pat. No. 5,525,520 issued on Jun. 11, 1996 to Dinh, discloses aphoto-activated, light emitting luminescence sensor and method ofdetecting trichloroethylene and related volatile organochloridecompounds wherein the compounds are directly dissociated by light.

U.S. Pat. No. 5,448,906 issued on Sep. 12, 1995 to Cheung, discloses anambient temperature, solid state, tin oxide (SnO), or zinc oxide (ZnO)sensor for the detection of oxygen which relies solely uponsorption/desorption.

U.S. Pat. No. 5,275,957 issued on Jan. 4, 1994 to Blades, et al.,discloses a method for using TiO₂'s photocatalytic properties to enhancethe disintegration rates of organics in waters.

None of the aforementioned references, however, discloses detecting adeposit, making quantitative determinations with respect to the deposit(i.e., identifying a contaminant and the quantity),“self”-decontaminating the deposit, and determining when chemicaldecontamination/neutralization is complete.

A need exists in the art for a device and method to detect a substance,make quantitative measurements regarding the substance, detoxify oralter the substance, and indicate when substance (toxic) neutralizationis complete. The device and method should perform these functions inreal-time or near real-time, so as to facilitate in-situ triagedecisions at contaminated sites.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a surface and methodfor detecting a deposit of a substance, making quantitativedeterminations with respect to the deposit (i.e., identifying acontaminant and the quantity) and decontaminating the deposit whichovercomes many of the disadvantages of the prior art.

Another object of the present invention is to provide a surface tofacilitate rapid detection and detoxification of a moiety contacting thesurface. A feature of the surface is the utilization of various exitedstates of semiconductors comprising the surface to determine thepresence, quantity and alteration of the moiety. An advantage of thesurface is that the aforementioned determination occurs upon excitationof the semi-conductor.

Embodiments of the present invention relate to a detection anddecontamination system and method for identifying and makingquantitative determinations with respect to different deposits andcontaminants (gaseous organic moieties for example). More specifically,embodiments of the present invention relate to a system and method fordetecting, characterizing, quantifying and decontaminating chemical andbiological spills, releases or weapons.

In the event of a spill, terrorist attack, or other chemical and/orbiological release, it is critical to be able to rapidly detect thecomponents that have been released, determine the concentration of thecomponents, decontaminate the released components, and verify that thedecontamination efforts have been successful.

Embodiments of the invention include a “smart” surface that may beincorporated into fabrics, painted surfaces, etc. and used by themilitary for fast response and decontamination in combat situations orby the government in subway systems, air ventilation systems, and forother large surface areas that may require decontamination. The smartsurfaces can constantly monitor the atmosphere above them, and, ifcontamination occurs in the proximity of the smart surface, a signal istriggered that identifies the constituent and concentration, andinitiates self decontamination of the surface.

The smart surface system comprises a controller, a sensing portion and adecontamination portion. The controller contains information about theuncontaminated surface and at least one contaminant. The sensing portioncommunicates with at least the controller and the decontaminationportion of the system and is adapted to detect the deposit. Thedecontaminating portion communicates with at least the controller and isadapted to decontaminate at least a portion of the affected surface.

A method for identifying and making quantitative determinations withrespect to a deposit on at least a portion of a surface also isprovided. The method comprises sensing the deposit on the portion of thesurface and initiating decontamination of at least the portion of thesurface in near real-time. The method further comprises determining ifthe decontamination of at least the portion of the surface is complete.When complete, the method comprises terminating the decontaminationprocedure.

Still another embodiment relates to a method for identifying and makingquantitative determinations with respect to deposits on at least aportion of a surface. This embodiment of the method comprisesdetermining if the portion of the system is contaminated using anembedded sensing portion. Decontamination of at least the portion of thesystem is initiated using an embedded decontamination portion. Themethod further comprises determining if the portion is stilldecontaminated using the embedded sensing portion; and terminatingdecontamination of the portion.

These and other objects of the present invention, as well as theadvantages thereof, will become clearer from the description whichfollows.

DESCRIPTION OF THE DRAWING

Embodiments together with the above and other objects and advantages maybest be understood from the following detailed description of theembodiments illustrated in the drawings, wherein:

FIG. 1 depicts a block diagram of a detection and decontaminationsystem, in accordance with one embodiment of the present invention;

FIGS. 2A & 2B depict schematic representations of the detection anddecontamination system of FIG. 1 in accordance with one embodiment ofthe present invention;

FIG. 3 depicts a plan view of the detection and decontamination systemof FIG. 2A illustrating the detecting and sensing portions in dashedlines in accordance with one embodiment of the present invention;

FIG. 4 depicts a plan view in partial cross section of the detection anddecontamination system of FIG. 3 in accordance with one embodiment ofthe present invention;

FIG. 5 depicts a plan view of another embodiment of the detection anddecontamination system similar to that of FIG. 2A in accordance with oneembodiment of the present invention;

FIG. 6 depicts a plan view of another embodiment of the detection anddecontamination system similar to that of FIG. 2A in accordance with oneembodiment of the present invention;

FIG. 7 depicts a side elevational view in partial cross section of thedetection and decontamination system taken along line 7-7 of FIG. 2Aaccordance with one embodiment of the present invention;

FIG. 8 depicts a high level flow diagram illustrating one method offorming or fabricating the detection and decontamination systemillustrated in FIGS. 1-7 in accordance with one embodiment of thepresent invention;

FIG. 9 depicts a high level flow diagram illustrating one method ofdetecting and decontaminating a contaminant in accordance with oneembodiment of the present invention;

FIG. 10 depicts a detailed flow diagram illustrating one method ofdetecting and decontaminating a contaminant similar to that of FIG. 9 inaccordance with one embodiment of the present invention; and

FIG. 11 depicts a detailed flow diagram illustrating one method ofdetecting and decontaminating a contaminant similar to that of FIGS. 9and 10 in accordance with one embodiment of the present invention.

FIG. 12 depicts a schematic representation of the furnace firing profilefor platinum electrodes;

FIG. 13 depicts a schematic representation illustrating the linear sweepresponse of the TiO₂ sensor in accordance with one embodiment of thepresent invention; and

FIG. 14 depicts a schematic representation illustrating the response oftwo sensors in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the event of a spill, terrorist attack, or other chemical and/orbiological release, it is critical to rapidly detect the components thathave been released, their concentrations, decontaminate the releasedcomponents, and determine whether decontamination efforts have beensuccessful. Embodiments of the present invention relate to a system andmethod adapted to detect the presence of a deposit (i.e., acontaminant), determine what deposit is present and its concentration,and, in many instances, neutralize (detoxify) the deposit if it is acontaminant, and provide feedback that the deposit is neutralized.

FIG. 1 depicts a block diagram illustrating a detection anddecontamination system (alternatively referred to as“detection/decontamination system” or “system”), generally designated10, in accordance with one embodiment of the present invention. In thedepicted embodiment, the detection/decontamination system 10 comprisesan embedded contamination sensing means or portion 12 and an embeddeddecontamination means or portion 14 coupled to and communicating with acontroller 16. The “embedded” feature is meant to designate that amechanism extends below a visible surface of a substrate, or issubstantially encapsulated within the substrate.

In the illustrated embodiment, the sensing and decontamination portions12, 14 are shown coupled to the controller 16 via connections orcoupling means 18 and 20 respectively. In one embodiment, connection 18comprises one or more wires or cable, while connection 20 comprises oneor more fiber optic cables. Other embodiments are contemplated in whichthe sensing and decontamination portions 12, 14 wirelessly communicatewith the controller 16.

In the illustrated embodiment, controller 16 may comprise amicroprocessor or microcontroller. The controller 16 contains a bufferor other storage device 22 including a “lookup table” or “signaturelibrary.” The table/library 22 contains the background resistances atspecific temperatures of uncontaminated materials stored as a standardcurve.

FIGS. 2A and 2B depict alternate embodiments of the system 10.Embodiments of the present invention employ one or more thin films of asemiconductor (TiO₂ for example); light having wavelengths moreenergetic than the semiconductor's bandgap (388 nm light for TiO₂,sunlight, xenon light, and mercury lamps, for example) that can becarried by fiber optics to the system or be positioned above the sensingsurface; and microelectrodes to detect contaminants and to initiateself-decontamination of the system. More specifically, embodimentscomprise conductive films or mesh layers of microcircuits and scoredfiber optics embedded in a substrate (including but not limited toglass, ceramics, fabrics, painted surfaces, etc.).

FIG. 2A depicts system 10A (similar to system 10 in FIG. 1) comprising asubstrate or surface 30 (here depicted as a portion of a largersurface). The sensing portion 12 comprises microelectrodes, conductivefilms (thin films for example), and/or one or more mesh layers ofmicrocircuits 32 (alternatively referred to as “electrodes”) and one ormore semiconductor layers 34 (TiO₂ for example). In this embodiment, thedecontamination portion 14 comprises one or more microelectrodes,conductive films, semiconductor layers, and scored or unscored fiberoptics 36 (alternatively referred to as “optics”) to transmit light tothe semiconductor layers.

In at least one embodiment, the electrodes 32 are embedded in thesubstrate 30 and are coupled to and communicate with the controller 16via one or more connections 18. In the illustrated embodiment, thecontroller 16 includes an electrode source 38. The electrode 32periodically or continuously captures or measures at least theresistance of the coated surface 30. This information is transported ortransferred to the controller 16 via connections 18, where theinformation is compared to known background resistance in thetable/library 22 in near real-time. In at least one embodiment, theelectrodes 32 are adapted to measure the resistance and temperature ofthe surface 30 and transmit this information to the controller 16.

In the illustrated embodiment, the one or more semiconductor layersinclude one or more particles 40 of the semiconductor material 34. Theparticles 40 may comprise macroparticles, microparticles, ornanoparticles, or some combination thereof, of the semiconductormaterial. In one or more embodiments, the semi-conductor comprises ametal oxide semiconductor (titanium dioxide [TiO₂] for example) althoughother metal oxide semiconductors (SrTiO₃, ZnO, SrO, In₂O₃, GeO₂, Nb₂O₅,MoO₃, CeO₂, ThO₂, SnO₂, ZrO₂, VO₂, WO₃, CdS, and Fe₂O₃ for example) arecontemplated.

FIG. 2A further illustrates the controller 16 coupled to optics 36 whichtransmit light in the ultraviolet spectrum via one or more connections20. Like the electrodes 32, in one embodiment the optics 36 are embeddedin the substrate 30. Further, the optics 36 are adapted to transmitlight having a shorter wavelength than the semiconductor's bandgapenergy and (sunlight, xenon light, mercury lamps for example). Thetransmitted light initiates the reaction between the semiconductor andthe sorbed contaminant, allowing for self-decontamination (via oxidationor reduction) to occur. In one embodiment, the controller 16 includes alight source 42 adapted to generate light having a wavelength moreenergetic than (i.e., equal to or exceeding) the semiconductor's bandgapenergy (for example, 388 nm for TiO₂). However, it also is contemplatedthat optics 36 transmitting the light are only activated by the source42.

In operation, a chemical moiety becomes physisorbed or chemisorbed tothe surface 30. This physisorbtion or chemisorbtion changes at least thesurface resistance (or surface resistance and temperature) of the layers34 and/or particles 40 as measured by the electrodes 32. The systemmeasures the resistance and temperature. Data representative of themeasured resistance and temperature is compared to data containing thebackground resistances and temperatures of uncontaminated surfacematerials stored as a standard curve in the look-up table/library 22.

The measured changes trigger a feedback loop that: (I) indicates thesurface 30 is contaminated (i.e., the deposit is a contaminant); (2)proposes which moiety is present and the concentration thereof; (3)triggers the illumination of a light at the source 42, which isdispersed throughout the surface via the optics 36 (or alternativelytriggers a light source above the surface that illuminates the sensingsurface [inducing TiO₂ or semiconductor photocatalytic oxidation orreduction of the contaminant]); and (4) provides feedback to thecontroller 16 as to when the measured resistance matches the storedbackground resistance, indicating that the contaminant has been oxidizedor reduced (decontaminated) and desorbed from the surface 30.

FIG. 2B depicts a system 10B (similar to systems 10 and 10A of FIGS. 1and 2A). However, in this embodiment the system 10B comprises a wandhaving a handle 44. It is contemplated that in at least one embodiment,rather than having a fixed system part of a permanent fixture, thesystem 10B may be mobile. That is, system 10B may be used by an operatoras a mobile detection device to sense a contaminant and decontaminate anatmosphere.

FIG. 3 depicts a plan view of the detection and decontamination system10A of FIG. 2A. In this embodiment, dashed lines are used to indicatethe sensing and decontamination portions 12 and 14. More particularly,the dashed lines indicate the optics 36 are positioned substantiallyperpendicular to the electrodes 32. Optics, however, also can bepositioned in alternative angles and configurations to the surface.

FIG. 4 depicts a plan view in partial cross section of the detection anddecontamination system 10A similar to that of FIGS. 2A and 3. FIG. 4depicts a portion of the surface 30; layer 34 and particles 40 areremoved to illustrate the arrangement of the optics 40 and electrodes36. Again, the optics 36 are positioned substantially perpendicular toand below the electrodes 32, although other arrangements arecontemplated.

FIG. 5 depicts a plan view of another embodiment of the detection anddecontamination system 10A similar to that of FIGS. 2A and 3. In FIG. 5,the optics 36 are positioned substantially parallel to, and above, theelectrodes 32, although again other arrangements are contemplated.

FIG. 6 depicts a plan view of another embodiment of the detection anddecontamination system 10A similar to that illustrated in FIGS. 2A and3. FIG. 6 depicts the optics 36 positioned at a predetermined angle tothe electrodes 32, although again, other arrangements are contemplated.

FIG. 7 depicts a side elevational view of the system 10A and 10B inpartial cross section in accordance with one embodiment of the presentinvention. FIG. 7 illustrates that at least one of the sensing anddecontamination portions 12, 14 are embedded. Here, both the electrodes32 and optics 36 are covered.

FIG. 8 depicts a high level flow diagram illustrating one method,generally designated 100, of forming or fabricating thedetecting/decontamination system illustrated in FIGS. 1-7 in accordancewith one embodiment of the present invention. As illustrated, the method100 comprises forming or fabricating the detecting/decontaminationsystem including forming at least one “smart” surface adapted to detectcontamination (chemical contamination for example) in near real-time andcleanse itself. This surface may be incorporated into glass, fabrics,painted surfaces, etc. Embodiments may be used by the military for fastresponse and decontamination situations. It could also be implemented inair cleansing systems.

Method 100 comprises incorporating one or more circuits into asubstrate, designated block 110. In at least one embodiment, thesubstrate includes, but is not limited to, glass, ceramics, fabrics,painted surfaces, etc. Further, the one or more circuits compriseconductive films, microsensors, and/or mesh layers of microcircuitssimilar to that provided previously.

Method 100 further comprises incorporating one or more optics into thesubstrate, designated block 112. In at least one embodiment, the opticscomprise scored (or unscored) fiber optic cables adapted to transmitenergy (for example light having wavelengths more energetic than (equalto or exceeding) the bandgap energy of the semiconductor used includesuch sources as sunlight, xenon light, mercury lamps, etc.). The scoredfiber optics are embedded in the substrate (including but not limited toglass, ceramics, fabrics, painted surfaces, etc). Unscored fiber optics,illumination from above the sensing/decontaminating surface, or variouslength fiber optics incorporated into the surface are also consideredfor the illumination source.

FIG. 8 further depicts method 100 comprising coating at least thesubstrate and circuits with a semiconductor. More specifically, themethod 100 comprises coating at least one, but generally all, of thesubstrate, the circuits and the optics with the macroparticles,microparticles or nanoparticles of the semiconductor (a metal oxidesemiconductor, TiO₂ for example, although other metal oxidesemiconductors such as SrTiO₃, ZnO, SrO, In₂O₃, GeO₂, Nb₂O₅, MoO₃, CeO₂,ThO₂, SnO₂, ZrO₂, VO₂, WO₃, CdS, and Fe₂O₃ are contemplated). It isfurther contemplated that at least one of the substrate and circuits maybe coated or covered by a mixture comprising different semiconductors,different sized particles of the same semiconductor or different sizedparticles of different semiconductors.

FIG. 9 depicts one method, designated 200, of detecting toxics andtoxins on a surface (the smart surface) in near-real time, determiningthe concentration of the contaminants present, self-decontaminating thesurface, and providing feedback information as to when decontaminationprocess is complete. In the illustrated embodiment, method 200 comprisessensing a contaminant (toxics and/or toxins) physisorbed or chemisorbedonto one surface of the system for example (similar to that of one ofthe systems supra), designated block 210. Decontamination is initiated(self-decontamination for example), designated block 212. In oneembodiment, decontamination comprises triggering the illumination of alight with energy greater than that of the semiconductor's bandgapenergy at a source to initiate the semiconductor's decontaminationreaction.

The method 200 further comprises determining if the decontamination iscomplete, designated block 214. In one embodiment, the method comprisesproviding feedback as to when the measured resistance and temperaturematches the stored background resistance and temperature, whichindicates that the contaminant has been oxidized or reduced(decontaminated) and desorbed from the surface. Finally, thedecontamination is terminated, designated block 216. In one embodiment,the method 200 terminates after decontamination is terminated. However,it is contemplated that method 200 operates in a repetitive fashion.

FIG. 10 depicts one method, designated 300, of detecting toxics andtoxins on a surface in near-real time, determining the concentration ofthe contaminants present, self-decontaminating the surface, andproviding feedback information as to when the decontamination processesare complete. In the illustrated embodiment, method 300 comprisesdetermining if a portion of the system is contaminated by contaminant,designated block 310. The method 300 uses an embedded sensing portion todetermine if a contaminant has been physisorbed or chemisorbed onto onesurface thereof.

Decontamination is initiated (self-decontamination for example) for atleast a portion of the system using an embedded decontamination portion,designated block 312. In one embodiment, all the system surfaces aredecontaminated. However, at least one embodiment is contemplated whereinthe embedded decontamination portion only decontaminates that portion ofthe system that is contaminated.

The method 300 further comprises determining if the decontamination iscomplete, designated block 314. In this embodiment, the system uses theembedded sensing portion to provide feedback as to when the resistancematches the stored background resistance, which indicates that thecontaminant has been oxidized or reduced (decontaminated) and desorbedfrom the surface. Finally, the decontamination is terminated, designatedblock 316. In one embodiment, the method 300 terminates afterdecontamination is terminated. However, it is contemplated that method300 operates in a repetitive fashion.

FIG. 11 depicts one method, designated 400, of detecting the presence ofa deposit on a surface in near-real time, determining the concentrationof the deposit, determining if the deposit is a contaminant,self-decontaminating the surface, and providing feedback information asto when the decontamination process is complete. In the illustratedembodiment, method 400 comprises measuring the resistance andtemperature of at least one coated surface of the system, designatedblock 410. The method 400 uses an embedded sensing portion to measurethe resistance and temperature. In one embodiment, the resistance andtemperature are measured periodically. However, embodiments arecontemplated in which the resistance and temperature are continuouslymeasured.

The information (i.e., data representing the measured resistance andtemperature) is transferred or transmitted to the controller, designatedblock 414. The controller compares the transmitted information toinformation stored therein (in a lookup table/signature library in nearreal-time) to determine if the deposit is a contaminant and theconcentration of the deposit, designated block 414. In one embodiment,the information stored in the controller comprises the backgroundresistance and temperatures of uncontaminated materials as a standardcurve.

The system determines if the deposit is a contaminant ornon-contaminant, designated diamond 416. Comparison of the informationto signatures stored in the lookup table determines if the deposit is acontaminant or non-contaminant. If the deposit is a noncontaminant,method 400 may either terminate or measure resistance and temperature ofthe surface again in a repetitive fashion.

If the system determines that the information deems the sorbant is acontaminant, then the method 400 triggers an illumination source andinitiates decontamination, designated blocks 418 and 420 respectively.The illumination is dispersed through at least a portion of the system,designated block 420. In one embodiment, the illumination source isdispersed using at least one fiber optic cable embedded in the system.The illumination source also can be positioned above thesensor/decontamination surface.

FIG. 11 further illustrates that the method 400 further comprisesproviding feedback, designated block 422. In one embodiment, the methodprovides feedback as to when the resistance matches the storedbackground resistance, which indicates that the contaminant has beenoxidized or reduced (decontaminated) and desorbed from the surface.

Experimental Sensor Fabrication

An experimental sensor in accordance with one embodiment was fabricatedby first depositing a metal electrode as a paste containing the metal inan organic vehicle on a substrate's surface. The metalelectrode-substrate was air-dried and fired at about 825° C. to becertain that the organic vehicle was removed. The substrate was selectedfrom the group consisting of alumina, Al₂O₃. The metal was selected fromthe group consisting of gold, platinum, and silver. FIG. 12 depicts aschematic representation of a furnace firing profile for platinumelectrodes fabricated using this method. The electrodes were slowlyheated to about 825° C. over a period of one hour, maintained at thattemperature for more than an hour, and cooled to ambient temperature forapproximately two hours.

Semiconductor metal oxide was subsequently screened on top and aroundthe metal electrode as a paste via an organic vehicle. The metal oxidewas selected from the group consisting of tin (IV) oxide, SnO₂; zincoxide, ZnO; titanium (IV) oxide, TiO₂; cadmium sulfide, CdS; andzirconium oxide, ZrO₂. The entire sensor was air-dried and subsequentlyfired up to 350° C. for two hours, again to be certain the organicvehicle was removed. The metal electrode enables the metal oxide film tobe attached to external equipment and monitored while chemical reactionstake place on the metal oxide surfaces. The portions of the electrodesnot covered by the metal oxide were connected to wire leads leading to adata acquisition and signal processing system.

Specifically, a TiO₂ gas microsensor was prepared by first depositingdesired patterns of thick films (less than 5 μm) consisting of platinum(Heraeus Conductor Paste, Product LPI 11-4493) onto aluminum oxide,Al₂O₃ substrate using a pneumatic industrial thick-film screen printer(Presco Model 873 with Ikegami optics). After air-drying, the films werefired (in a Lindberg type 51524 furnace) according to the profiledepicted in FIG. 12. After cooling, a deposit of anatase TiO₂ (DegussaP25) was placed as a thick film (5 μm) mixed with Heraeus vehicleRV-025, 1.0 grams of TiO₂ to 6.5 grams RV-025. Antase TiO₂ was used asopposed to rutile TiO₂ because the anatase form is more reactive.

Measurement Example

Shielded electrical leads were connected to a TiO₂ sensor in a quartzreaction chamber. The sensor was positioned in the middle of thechamber. A rubber stopper covered in aluminum encased the leads andsealed the chamber. For the analysis of each gaseous organic moiety, thechamber was opened to the atmosphere and flushed with compressed zerochromatographic air for ten minutes at a rate greater than 10 liters perminute. The sensor was inserted into the quartz reaction chamber, sealedwith the stopper, and placed into a reactor (Rayonet PhotochemicalChamber Reactor RMR Model 600) containing eight ultraviolet (UV) lightsproducing 253.7 nanometer light, providing a quantum yield of 0.100Einstein per minute.

A cyclic potential sweep was applied to the sensor from −5.00V to +5.00Vproducing a residual current curve. The system used to gather the TiO₂sensor response data was composed of commercial-off the shelf hardwareand proprietary voltammetry software. The system allowed completecontrol over the applied potential sweep and acquisition to capturephotocatalytic responses and the concomitant electrical responses. Acomplete signature was captured for each experimental run. Either all ofthe voltammogram or the linear sweep section (negative potential topositive potential) was used for sensor evaluation.

TABLE 1 illustrates saturation concentrations of six differentcontaminant gases used in the experimental runs. The amount of eachcontaminant used was such that the volume around the sensor wassaturated with the contaminant at the given ambient pressure andtemperature.

TABLE 1 Concentrations¹ of contaminant gases Compound Maximumconcentration (ppm)² Methylene Chloride, CH₂Cl₂ 464,000 Ethanol, C₂H₆O59,00 Benzene, C₆H₆ 126,000 Isopropanol, C₃H₈O 43,000 Xylene, C₈H₁₀13,000 Acetone, C₃H₆O 285,000 ¹Satuation concentrations were calculatedfrom contaminant vapor pressures ²ppmv is parts per million volume

FIG. 13 depicts a schematic representation illustrating the linear sweepresponse of the TiO₂ sensor. In this figure, the linear sweep responseis a plot of current in amperes versus applied potential difference involts, to saturated concentrations of the six organic moieties providedin Table 1 in a zero chromatographic air atmosphere. Only one quadrantof the voltammogram is shown to simplify the response signal. Both thevoltage and the current are direct. As may be seen in FIG. 13, distinctresponses are obtained from the TiO₂ sensor as it is exposed tosaturated concentrations of various constituents in air. Uniquelydifferent responses are obtained for each contaminant as eachcontaminant, due to its different electronic and physical structure, hasa different reaction with and effect upon the sensor's surface.

FIG. 14 depicts a schematic representation illustrating the response oftwo sensors, as a plot of current in amperes to applied potentialdifference in volts, to methylene chloride, CH₂Cl₂, in the presence ofultraviolet light. The curves depicted in FIG. 14 illustrate threeresponses: 1) the response of a newly fabricated sensor (designatedsensor “8”) to methylene chloride, 2) the response of the sensor 8 tomethylene chloride a week after the initial test was performed, and 3)the response of a different sensor (designated “sensor 3”) to methylenechloride. Sensor 8 had previously been used twice to detect isopropanol.As seen in FIG. 14, the three responses are essentially identical.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

1. A method for identifying and making quantitative determinations withrespect to a deposit on at least a portion of a surface, the methodcomprising: a. sensing the deposit on the portion of the surface; b.initiating decontamination of at least the portion of the surface innear realtime; c. determining said decontamination of at least theportion of the surface is complete; and d. terminating saiddecontamination.
 2. The method as recited in claim 1 wherein steps a)through d) are performed in a repetitive fashion as a means tocontinually self decontaminate the surface.
 3. The method as recited inclaim 1 comprising measuring resistance and temperature of the portionof the surface having the deposit using an embedded sensing portion. 4.The method as recited in claim 3 comprising comparing said measuredresistance and temperature with stored data of resistance andtemperature values of predetermined moieties.
 5. The method as recitedin claim 4 comprising determining the deposit is a contaminant based onsaid comparison prior to initiating decontamination.
 6. The method asrecited in claim 2 wherein initiating said decontamination comprisesilluminating a light having energy greater than the semiconductor'sbandgap energy, thereby decontaminating at least the portion of thesurface.
 7. A method for identifying and making quantitativedeterminations with respect to deposits on at least a portion of asurface, the method comprising: a. determining the portion of the systemis contaminated using an embedded sensing portion; b. initiatingdecontamination of at least the portion of the system using an embeddeddecontamination portion; c. determining the portion is decontaminatedusing the embedded sensing portion; and d. terminating decontaminationof the portion.
 8. The method of claim 7 wherein steps a) through b) areperformed in a repetitive fashion.
 9. The method as recited in claim 7comprising measuring resistance and temperate of the portion of thesurface having the deposit using an embedded sensing portion.
 10. Themethod as recited in claim 9 comprising comparing said measuredresistance and temperature with a stored resistance and temperature,thereby determining the deposit is a contaminant.
 11. The method asrecited in claim 1 wherein the step of sensing the deposit initiatesself decontamination of the surface.
 12. The method as recited in claim7 wherein the step of determining the portion of the system contaminatedinitiates self decontamination of the system.